Survival of bicompartmental knee arthroplasty at 5 to 23 years

Functional outcome after bicompartmental knee replacement for medial and patellofemoral osteoarthritis

INTRODUCTION

Total knee arthroplasty (TKA) is used for tricompartmental knee osteoarthritis, while unicompartmental knee arthroplasty (UKA) is preferred for unicompartmental knee osteoarthritis. Bicompartmental knee arthroplasty (BKA) aims to address 2 knee compartments by combining 2 UKA's or 1 UKA with a patellofemoral replacement. This study examines the clinical outcomes of BKA, focusing on pain alleviation and knee function. The aim of this study is to report the functional outcome of BKA and see if this aligns with BKA outcomes from literature in terms of patient reported outcome measurements (PROMs) and range of motion (ROM) after a 2-year follow-up. Additionally, radiographic alignment, implant survivorship, adverse events and length of stay are secondary outcomes.

METHODS

This is a cohort study of 21 patients who underwent BKA for medial and patellofemoral osteoarthritis. The patients had follow-up for at least 2 years postoperatively. PROMs were assessed using the Knee injury and Osteoarthritis Outcome Score (KOOS), Knee Society Score (KSS), Oxford Knee Score, Western Ontario and McMaster University Osteoarthritis index (WOMAC) and the Visual Analogue Scale (VAS). ROM was measured using a goniometer. Pre- and postoperative radiographic coronal alignment was measured using standard full leg radiographs. Patient demographics, implant survivorship, length of stay and adverse events were recorded.

RESULT

Twenty-one patients (23 knees) were included, with a mean follow-up of 41 months (standard deviation [SD] 12 months; range 24-59 months). Patient-reported outcome measures (PROMs) demonstrated significant improvements, with 80% achieving good to excellent OKS and KSS scores. KOOS scores were similar to scores found in literature. The WOMAC score was higher in our results compared to other authors. Which indicates worse outcome. The mean preoperative hip-knee-ankle angle (HKAA) was 2.4 degrees varus (SD 1.9 degrees; range 1.2 degrees valgus - 6.1 degrees varus), while the mean postoperative HKAA was 0.3 degrees valgus (SD 2.8 degrees; range 4.6 degrees valgus - 5.6 degrees varus) (p < 0.001). Postoperative range of motion averaged 117 degrees (SD 10 degrees; range 98-132).

CONCLUSIONS

BKA shows promise in alleviating pain and improving knee function in patients with medial and patellofemoral osteoarthritis. Challenges include the risk of revision and technical difficulties during surgery. Comparative studies suggest similar outcomes between BKA and TKA, with potential advantages for younger, more active patients. Further research, particularly randomized trials with larger cohorts, is necessary to elucidate the long-term benefits and drawbacks of BKA compared to other knee arthroplasty options.

Patello-femoral arthroplasty- indications and contraindications

Patellofemoral arthroplasty (PFA) is emerging as an attractive alternative to total knee arthroplasty (TKA) for isolated patellofemoral-osteoarthritis (PF-OA) for selected patients. The success of PFA is highly dependent on patient selection. This intervention is still burdened with a higher rate of revisions and a lower survival rate than TKA when the indications or the surgical technique are not optimal. We highlight the indications and contraindications of PFA to obtain satisfying functional outcomes and survivorship. Preoperative clinical and radiological assessment is critical to determine the presence of PFA indications, the absence of contraindications and the necessity of any associated procedures, particularly for the tibial tubercle. The typical indications are patients with isolated symptomatic PF-OA, with trochlear dysplasia, when bone-on-bone Iwano 4 osteoarthritis is observed, without significant malalignment and with the absence of risk factors for developing progressive tibiofemoral-OA. The three main causes of isolated PF-OA are primary OA, trochlear dysplasia and posttraumatic OA following patellar fracture. Trochlear dysplasia is the preferred indication for PFA. Lack of experience with arthroplasty or realignment of the extensor mechanism is a relative contraindication to performing PFA.

The Influence of Patello-Femoral Overstuffing After Modular Unlinked Bicompartmental Knee Arthroplasty (BiKA) for Medial Tibio-Femoral and Patello-Femoral Osteoarthritis of the Knee

BACKGROUND

The factors affecting results after bicompartmental knee arthroplasty (BiKA) have not been fully elucidated. This major ligament-preserving procedure may be more susceptible to overstuffing of the patello-femoral (PF) joint than the major ligament-sacrificing total knee arthroplasty. Currently, we investigated the effect of PF overstuffing after BiKA on its clinical outcome.

METHODS

There were 71 patients (74 knees) who underwent modular unlinked BiKA at our clinic who had a follow-up of 5 to 9 years. Final follow-up results were assessed by evaluating knee range of motion, the 2011 Knee Society Score (2011KSS), Japanese Knee Osteoarthritis Measure, and radiological findings. The degree of postoperative PF overstuffing was evaluated by computed tomography and magnetic resonance images for 55 knees, and the correlation between the degree of overstuffing and postoperative clinical results were examined.

RESULTS

Overall clinical results improved significantly after surgery without any revision cases. The X-ray measurements showed the improved coronal alignments and the appropriate implant installation angles. Higher degree of postoperative PF overstuffing caused by insufficient amount of osteotomy on the anterior surface of the femur correlated with worse postoperative total 2011KSS at 2 years after surgery (Spearman's rank correlation coefficient (rs) = -0.387, P = .004), as opposed to no correlation at the time of the final follow-up (Spearman's rank correlation coefficient = 0.068, P = .623).

CONCLUSION

Modular unlinked BiKA provided patients with a high level of satisfaction and functional improvement over 5 to 9 years postoperatively. However, because PF overstuffing affects initial patient satisfaction, the amount of osteotomy should be determined carefully during the surgery.

Painful Unicompartmental Knee Arthroplasty: Etiology, Diagnosis and Management

Unicompartmental knee arthroplasty (UKA) is an increasingly common procedure. Patients with persistent or new postoperative pain can present a challenge for surgeons to accurately diagnose and treat. The purpose of this study is to provide a comprehensive review of the presentation, diagnosis, and management of the various pathologies contributing to pain after UKA. The most common causes of a painful UKA include aseptic component loosening and progression of osteoarthritis. Both of these conditions may be treated with either revision UKA or conversion to total knee arthroplasty. While technically challenging, these procedures are often associated with favorable outcomes. Other causes of pain after UKA include infection, atraumatic tibial component subsidence, periprosthetic fracture and malalignment. Careful clinical, radiographic, and laboratory evaluation is therefore critical to accurately identify the source of pain and guide appropriate management.

Outcome of simultaneous bi-unicompartmental knee arthroplasty: a systematic review

BACKGROUND AND AIM

Simultaneous medial and lateral tibiofemoral osteoarthritis (OA) could be treated with bi-unicompartmental knee arthroplasty (Bi-UKA) as an alternative to total knee arthroplasty (TKA). The present systematic review aims to assess if simultaneous Bi-UKA is a feasible option for treating medial and lateral tibiofemoral OA.

MATERIALS AND METHODS

A comprehensive search of PubMed, MEDLINE, Cochrane Library, and Google Scholar was performed to find studies that reported on the outcome of simultaneous Bi-UKA for both medial and lateral tibiofemoral OA.

RESULTS

Seven studies were considered eligible for inclusion in the present systematic review. Intraoperative fractures occurred 8 times. Overall, there were 22 revisions of the prosthetic components for any reason with a survival rate that ranged from 83 to 100%. Of these, 16 revisions were for the aseptic loosening of the prosthetic components. Out of 302 surgeries, three were revised due to symptomatic OA progression in the patello-femoral joint. All clinical scores improved at the latest follow-up compared to preoperative values. Moreover, there were no differences in clinical scores of Bi-UKA compared to unicompartmental knee arthroplasty (UKA), or medial UKA plus patello-femoral prosthesis. Whereas, compared to TKA, Bi-UKA patients had comparable or superior scores. Finally, the Bi-UKA group had a significantly shorter hospital stay compared to the TKA group.

CONCLUSIONS

The use of simultaneous Bi-UKA is a valid option to address bicompartmental knee OA in selected patients with low intraoperative fracture rate, low revision rate, satisfactory clinical outcome, and fast recovery.

Image-based robot assisted bicompartmental knee arthroplasty versus total knee arthroplasty

OBJECTIVE

To evaluate the short-term clinical outcomes of image-based robot-assisted bicruciate retaining bicompartmental knee arthroplasty and compare it to robot-assisted total knee arthroplasty in the Indian population.

METHODS

Between December 2018 and November 2019, five patients (six knees) underwent robot-assisted bicompartmental knee arthroplasty (BCKA). These patients were demographically matched with five patients (six knees) who underwent robot-assisted total knee arthroplasty (TKA) during the same period. Clinical outcomes of these twelve knees were assessed in the form of knee society score (KSS) score, Oxford knee score (OKS), and forgotten joint score (FJS) after a minimum follow-up period of 25 months. The data between the two cohorts were compared and analyzed.

RESULTS

Scores obtained from both cohorts were subjected to statistical analysis. SPSS software was utilized and the Mann Whitney U-test was utilized to compare the two groups. There was no statistically significant difference found between the two groups in terms of functional outcome.

CONCLUSION

Image-based robot-assisted BCKA is a bone stock preserving and more physiological procedure which can be a promising alternative to patients presenting with isolated arthritis of only two compartments of the knee. Although long-term, larger trials are warranted to establish it as an alternative, our pilot study shows an equally favorable outcome as TKA, making it an exciting new avenue in the field of arthroplasty.

Medial bicompartmental arthroplasty patients display more normal gait and improved satisfaction, compared to matched total knee arthroplasty patients

PURPOSE

Medial bicompartmental arthroplasty, the combination of ipsilateral medial unicompartmental and patellofemoral arthroplasty, is an alternative to total knee arthroplasty for patients with medial tibiofemoral and severe patellofemoral arthritis, when the lateral tibiofemoral compartment and anterior cruciate ligament are intact. This study reports the gait and subjective outcomes following medial bicompartmental arthroplasty.

METHODS

Fifty-five subjects were measured on the instrumented treadmill at top walking speeds, using standard metrics of gait. Modular, single-stage, medial bicompartmental arthroplasty subjects (n = 16) were compared to age, body mass index, height- and sex-matched healthy (n = 19) and total knee arthroplasty (n = 20) subjects. Total knee arthroplasty subjects with pre-operative evidence of tricompartmental osteoarthritis or anterior cruciate ligament dysfunction were excluded. The vertical component of ground reaction force and temporospatial measurements were compared using Kruskal-Wallis, then Mann-Whitney test with Bonferroni correction (α = 0.05). Oxford Knee and EuroQoL EQ-5D scores were compared.

RESULTS

Objectively, the medial bicompartmental arthroplasty top walking speed of 6.7 ± 0.8 km/h was 0.5 km/h (7%) slower than that of healthy controls (p = 0.2), but 1.3 km/h (24%) faster than that of total knee arthroplasty subjects (5.4 ± 0.6 km/h, p < 0.001). Medial bicompartmental arthroplasty recorded more normal maximum weight acceptance (p < 0.001) and mid-stance forces (p = 0.03) than total knee arthroplasty subjects, with 11 cm (15%) longer steps (p < 0.001) and 21 cm (14%) longer strides (p = 0.006). Subjectively, medial bicompartmental arthroplasty subjects reported Oxford Knee Scores of median 41 (interquartile range 38.8-45.5) compared to total knee arthroplasty Oxford Knee Scores of 38 (interquartile range 30.5-41, p < 0.02). Medial bicompartmental arthroplasty subjects reported EQ-5D median 0.88 (interquartile range 0.84-0.94) compared to total knee arthroplasty median 0.81 (interquartile range 0.73-0.89, p < 0.02.) CONCLUSION: This study finds that, in the treatment of medial tibiofemoral osteoarthritis with severe patellofemoral arthritis, medial bicompartmental arthroplasty results in nearer-normal gait and improved patient-reported outcomes compared to total knee arthroplasty.

LEVEL OF EVIDENCE

III.

The compartmental approach to revision of partial knee arthroplasty results in nearer-normal gait and improved patient reported outcomes compared to total knee arthroplasty

PURPOSE

This study investigated the gait and patient reported outcome measures of subjects converted from a partial knee arthroplasty to combined partial knee arthroplasty, using a compartmental approach. Healthy subjects and primary total knee arthroplasty patients were used as control groups.

METHODS

Twenty-three patients converted from partial to combined partial knee arthroplasty were measured on the instrumented treadmill at top walking speeds, using standard gait metrics. Data were compared to healthy controls (n = 22) and primary posterior cruciate-retaining total knee arthroplasty subjects (n = 23) where surgery were performed for one or two-compartment osteoarthritis. Groups were matched for age, sex and body mass index. At the time of gait analysis, combined partial knee arthroplasty subjects were median 17 months post-revision surgery (range 4-81 months) while the total knee arthroplasty group was median 16 months post-surgery (range 6-150 months). Oxford Knee Scores and EuroQol-5D 5L scores were recorded at the time of treadmill assessment, and results analysed by question and domain.

RESULTS

Subjects revised from partial to combined partial knee arthroplasty walked 16% faster than total knee arthroplasty (mean top walking speed 6.4 ± 0.8 km/h, vs. 5.5 ± 0.7 km/h p = 0.003), demonstrating nearer-normal weight-acceptance rate (p < 0.001), maximum weight-acceptance force (p < 0.006), mid-stance force (p < 0.03), contact time (p < 0.02), double support time (p < 0.009), step length (p = 0.003) and stride length (p = 0.051) compared to primary total knee arthroplasty. Combined partial knee arthroplasty subjects had a median Oxford Knee Score of 43 (interquartile range 39-47) vs. 38 (interquartile range 32-41, p < 0.02) and reported a median EQ-5D 0.94 (interquartile range 0.87-1.0) vs. 0.84 (interquartile range 0.80-0.89, p = 0.006).

CONCLUSION

This study finds that a compartmental approach to native compartment degeneration following partial knee arthroplasty results in nearer-normal gait and improved patient satisfaction compared to total knee arthroplasty.

LEVEL OF EVIDENCE

III.

Robotic Assisted Patellofemoral Joint Replacement: Surgical Technique, Tips and Tricks

In this article we wish to provide MAKO robotic knee users a surgical guide including tips and tricks on performing MAKO robotic-assisted patellofemoral joint replacements. The senior authors in this paper from the Exeter Knee Reconstruction Unit, United Kingdom are highly experienced MAKO users who have been performing MAKO assisted Patellofemoral joint replacements since 2017.

Arthroscopic-assisted robotic bi-unicompartmental knee arthroplasty: a pilot cadaveric study

INTRODUCTION

Although bicondylar arthroplasty showed great functional results, it encounters some difficulties to be performed routinely. On the other hand, arthroscopic techniques tend to replace open surgical techniques in sports medicine but strive to be developed in the field of arthroplasty. This study aimed to assess the feasibility of a micro-invasive bi-compartmental knee arthroplasty using both arthroscopic and robotic technologies (A-BiUKA).

MATERIALS AND METHODS

The study was conducted on complete fresh-frozen and embalmed cadaveric specimens. The main criterion of judgment was the successful positioning of trial implants through a minimal quad-sparing approach. Arthroscopy was used for bone-morphing and burring, supported by an image-free robotic system. Secondary criteria of judgment were axial deviation (measured using the navigation system), operating time, and incision length.

RESULTS

Ten A-BiUKA were performed. Implantation was successful in all cases. The mean preoperative frontal deviation was 179.8° ± 3.2 [175: 185], the mean postoperative frontal deviation was 178.5° ± 2.2 [175: 182], without any outliers. The mean correction was 1.7° ± 1.6 [0: 5]. Once the eight first A-UKA were performed, constituting the learning curve, the mean operative time for the remaining twelves surgeries was 90 min ± 6. The mean skin incision length was 3.35 cm ± 0.13 [3: 4].

CONCLUSION

Associated arthroscopic and robotic technologies allows to perform Bi-UKA procedure using a quad sparing mini-invasive approach. Clinical prospective studies have to confirm the feasibility and the clinical outcomes of this surgery.

Patellofemoral arthroplasty in combination with high tibial osteotomy can achieve good outcome for patients with medial-patellofemoral osteoarthritis

Background

The purpose of our study is to report on the clinical outcomes of patients who undergoing patellofemoral arthroplasty (PFA) in combination with a high tibial osteotomy (HTO). Due to this procedure's conservative and kinematics-preserving characteristics, we hypothesized that PFA in combination with HTO would result in good clinical outcomes in patients with medial and patellofemoral compartment osteoarthritis (MPFOA).

Methods

Patients who underwent PFA in combination with HTO for MPFOA from January 2018 to April 2020 were included in the study. Clinical outcomes were analyzed by comparing the Knee Society Score, Oxford Knee Score, Range of Motion, and Forgotten Joint Score before and after the procedure. Radiological evaluations were also performed to assess the tibiofemoral osteoarthritis progression and implant loosening. For all tests, the value of p < 0.05 was considered statistically significant.

Results

A total of nine consecutive patients who underwent PFA in combination with HTO were included. Two were males, seven were females. The average follow-up period was 2.6 ± 0.4 years. Clinical outcomes showed a significant improvement in the Knee Society Score (clinical score: 90.3 ± 8.5 and function score: 90.8 ± 7.8), Oxford Knee Score (43.6 ± 3.6), Forgotten Joint Score (71.2 ± 10.2), and knee Range of Motion (130.4 ± 8.1°) at the final follow-up. Additionally, hip-knee-ankle angle significantly decreased from -9.3 ± 2.1° preoperatively to 2.2 ± 1.2° at the final follow-up (p < 0.05). There were no complications for any patient during the follow-up time.

Conclusion

This study shows that patients who underwent PFA in combination with HTO for the treatment of MPFOA achieved good clinical and radiological outcomes. This combined surgery could be an effective alternative to treat MPFOA in well-selected patients.

Disease Progression After Unicompartmental Arthroplasty: Add a Compartment or Revise to Total Knee Arthroplasty?

BACKGROUND

Five percent to 7% of unicompartmental knee arthroplasties (UKA) require revision for disease progression in untreated compartment(s), most commonly to total knee arthroplasty (TKA). TKA requires removal of bone and usually the anterior cruciate ligament. Preserving the UKA and converting to a bicompartmental arthroplasty (BCA) by performing a second UKA is an alternative.

METHODS

The results of 73 UKA-BCA patients were compared to 75 patients treated by UKA-TKA revision. Knee Society, Knee Osteoarthritis Outcome Score Joint Replacement, and patient satisfaction scores were collected by a blinded therapist. Patients were asked about their implant preference and recovery. Twenty-two UKA-BCA revision patients had a UKA (6) or TKA (16) in the contralateral knee; thus, a direct comparison of UKA-BCA to both UKA and TKA was possible.

RESULTS

Of the UKA-BCA patients, 69 (94%) had excellent or good, 2 (3%) fair, and 2 (3%) poor outcomes with 1 patient requiring revision to TKA. Of patients with a TKA in the contralateral knee, 13 (81%) preferred the UKA-BCA replacement and 3 (19%) preferred the TKA. All patients said the UKA-BCA revision recovery was similar or easier than their initial UKA. Of UKA-TKA revisions, 59 (79%) had excellent or good, 9 (12%) fair, and 7 (9%) poor outcomes. There was 1 wound infection and 1 re-revision in the UKA-BCA group and 1 wound infection and 3 re-revisions in the UKA-TKA group. The Knee Osteoarthritis Outcome Score Joint Replacement and Knee Society Scores were better for UKA-BCA compared to UKA-TKA.

CONCLUSION

UKA-BCA is a successful treatment for disease progression following UKA.

Journey-Deuce bicompartmental knee arthroplasty with the addition of computer navigation achieves good clinical outcomes and implant survival at 10 years

PURPOSE

To report 10-year outcomes and survivorship in patients undergoing bicompartmental knee arthroplasty (BCKA) using the Journey-Deuce prosthesis in a consecutive prospective case series.

METHODS

Between November 2006 and November 2009, 41 patients with a mean age of 69.6 years (range 51-86) underwent 51 bicompartmental knee arthroplasties with the Journey-Deuce knee prosthesis. All patients presented with symptomatic medial and patellofemoral compartment osteoarthritis, with intact cruciate ligaments and a preserved lateral compartment on plain radiographs and Magnetic Resonance Imaging. Clinical assessment was undertaken pre-surgery and at 1, 2, 5 and 10 years post-surgery using the Oxford Knee Score (OKS), EuroQol Group 5-Dimension self-reported questionnaire (EQ-5D) and maximal active range of motion (ROM).

RESULTS

30 patients (37 knees) were followed-up at a mean time of 11.4 years (SD 1.1; range 10.5-14.0). Eight patients (ten knees) were deceased and three could not be contacted at final review. No major component revision was performed. Pre-operative OKS 25.4 (SD 5.2; range 15-40), knee flexion 116.4° (SD 10.3°; range 100°-140°) and EQ-5D 70.5 (SD 19.9; range 25-95). 10-year OKS 43.5 (SD 4.1; range 32-48), knee flexion 127.3° (SD 11.1°; range 105°-144°) and EQ-5D 77.4 (SD 9.3; range 60-100). The OKS (p < 0.0001), EQ-5D (p = 0.024) and active knee flexion ROM (p < 0.0001) all significantly improved from pre-surgery to 1-year post-surgery, with no further significant changes in these scores between any post-operative time period up until 10 years. 32% (7/22) of tibial and 45% (10/22) of femoral components showed progressive radiolucencies between 2 and 5-year and 10-year follow-up.

CONCLUSIONS

This is the largest cohort of patients having undergone BCKA (with the Journey-Deuce prosthesis) with longest follow-up described in the literature. At 10 years, patients presented with significantly improved clinical outcomes, comparable to other surgical arthroplasty options. No major component revision was performed. Progressive radiolucencies were noted in 32% of tibial and 45% of femoral components without corresponding clinical signs of loosening.

LEVEL OF EVIDENCE

Level III.

The risk of tibial eminence avulsion fracture with bi-unicondylar knee arthroplasty : a finite element analysis

AIMS

The aim of this study was to determine the risk of tibial eminence avulsion intraoperatively for bi-unicondylar knee arthroplasty (Bi-UKA), with consideration of the effect of implant positioning, overstuffing, and sex, compared to the risk for isolated medial unicondylar knee arthroplasty (UKA-M) and bicruciate-retaining total knee arthroplasty (BCR-TKA).

METHODS

Two experimentally validated finite element models of tibia were implanted with UKA-M, Bi-UKA, and BCR-TKA. Intraoperative loads were applied through the condyles, anterior cruciate ligament (ACL), medial collateral ligament (MCL), and lateral collateral ligament (LCL), and the risk of fracture (ROF) was evaluated in the spine as the ratio of the 95^th percentile maximum principal elastic strains over the tensile yield strain of proximal tibial bone.

RESULTS

Peak tensile strains occurred on the anterior portion of the medial sagittal cut in all simulations. Lateral translation of the medial implant in Bi-UKA had the largest increase in ROF of any of the implant positions (43%). Overstuffing the joint by 2 mm had a much larger effect, resulting in a six-fold increase in ROF. Bi-UKA had ~10% increased ROF compared to UKA-M for both the male and female models, although the smaller, less dense female model had a 1.4 times greater ROF compared to the male model. Removal of anterior bone akin to BCR-TKA doubled ROF compared to Bi-UKA.

CONCLUSION

Tibial eminence avulsion fracture has a similar risk associated with Bi-UKA to UKA-M. The risk is higher for smaller and less dense tibiae. To minimize risk, it is most important to avoid overstuffing the joint, followed by correctly positioning the medial implant, taking care not to narrow the bone island anteriorly.Cite this article: Bone Joint Res 2022;11(8):575-584.

Outcomes of Bi-unicompartmental Versus Total Knee Arthroplasty for the Treatment of Medial and Lateral Knee Osteoarthritis: A Systematic Review and Meta-analysis of Comparative Studies

PURPOSE

The aim of this meta-analysis was to evaluate differences in functional outcomes between simultaneous bi-unicompartmental knee arthroplasty (Bi-UKA) and total knee arthroplasty (TKA) for the treatment of medial and lateral knee osteoarthritis.

MATERIAL AND METHODS

According to the PRISMA statement, a comprehensive search was conducted to identify studies reporting comparative results of the Bi-UKA versus the TKA. Of 953 titles, 6 studies met the inclusion criteria.

RESULTS

A total of 286 patients were identified, of which 137 underwent Bi-UKA and 149 TKA. TKA reported a mean hip-knee-ankle (HKA) angle of 179.4 ± 2.4 compared to that in Bi-UKA measuring 177.2 ± 2.7 (p = 0.0001, 95% CI - 3.02 to - 1.38). No difference was found in the Western Ontario and McMaster Universities (WOMAC) pain (4 ± 1.6 and 4.2 ± 1.3 for Bi-UKA and TKA, respectively; p = 0.4996, 95% CI - 0.86 to 0.43). Bi-UKA was favorable in terms of WOMAC function (7.5 ± 1.9 and 9 ± 1.9 for Bi-UKA and TKA, respectively; p = 0.001, 95% CI - 2.29 to - 0.61) and WOMAC stiffness (1.6 ± 1 and 2.4 ± 0.7 for Bi-UKA and TKA, respectively; p = 0.0001, 95% CI - 1.18 to - 0.42). Bi-UKA showed a better Knee Society Score (KSS) in comparison to TKA (79.7 ± 7.8 and 75.4 ± 10.5 for Bi-UKA and TKA, respectively; p = 0.0021, 95% CI 1.58-7.02). The differences in postoperative outcomes scores between Bi-UKA and TKA were lower than their respective minimum clinically important differences.

CONCLUSIONS

When Bi-UKA and TKA are compared for the treatment of medial and lateral knee osteoarthritis, Bi-UKA are favorable in terms of WOMAC and KSS even though these values are lower than the minimum clinically important differences; moreover, similar postoperative hip-knee-ankle angle can be expected 3 years after Bi-UKA and TKA.

Combined procedures with unicompartmental knee arthroplasty: High risk of stiffness but promising concept in selected indications

Introduction: Unicompartmental knee arthroplasty (UKA) has traditionally been contraindicated in the presence of an ACL deficient knee, bi-compartmental disease, or significant coronal deformity due to concerns regarding increased risk of persisted pain, knee instability, tibial loosening, or progression of osteoarthritis. The aim of this study was to evaluate the outcomes of patients undergoing UKA with an associated surgical procedure in these specific indications. Method: This was a retrospective cohort study of patients undergoing UKA between December 2015 and October 2020. Patients were categorized into groups based on associated procedures: UKA + ACL, UKA + HTO, and bicompartmental arthroplasty. Outcomes were assessed using the Knee Society Score (KSS) knee and function scores and the Forgotten Joint Score. Radiological and complication analysis was performed at the last clinical follow-up. Results: Thirty-two patients (13 men and 19 women) were included. The mean age was 56.2 years ± 11.1 (range, 33–84) with a mean follow-up of 26.3 months ± 15 (7.3–61.1). There was a significant improvement between the pre-and postoperative KSS Knee (+34.3 ± 16.5 [12–69]), Function (+34.3 ± 18.6 [0–75]), and Total scores (+68.5 ± 29.4 [24–129]) (p = 0.001). Seven patients (21.8%) required an arthroscopic arthrolysis for persistent stiffness. Two patients (UKA + PFA and UKA + ACL) underwent revision to TKA. Patient satisfaction was 90%, and mean flexion at last follow-up was 122° ± 6 (120–140). The implant survival rate was 94%. Discussion: This study found performing UKA with an additional procedure to address relative contraindications to the arthroplasty in physically active patients with monocompartmental knee arthritis is an efficient strategy with good results at short-term follow-up. It should be reserved for patients where TKA is likely to have unsatisfactory results, and the patient has been fully counseled regarding the management options. Even if there is a high rate of complications with stiffness requiring a re-intervention, the final results are very satisfying with no impact of the reintervention on the clinical result in the short term.

Relevant changes of leg alignment after customised individually made bicompartmental knee arthroplasty due to overstuffing

PURPOSE

The purpose of this study is to analyse the change in knee alignment after customised individually made (CIM) bicompartmental knee arthroplasty (BKA) and the subsequent consequences for patellar tracking.

METHODS

Medical records of 23 patients who received 26 CIM BKA (ConforMIS iDuo G2) at our clinic between November 2015 and July 2018 were reviewed. The objective part of the Knee Society Score (KSS), the hip-knee-ankle angle (HKA), the tibial mechanical angle (TMA) and femoral mechanical angle (FMA) were recorded preoperative and four months postoperative. Leg alignment was classified as neutral (HKA = 180° ± 3°), varus (HKA < 177°) or valgus (HKA > 183°). Furthermore, patellar tracking was determined on skyline view radiographs and adverse events were recorded. Implant survival rate was determined with the Kaplan-Meier method. Patient-reported outcome measures (PROMs) were pain, satisfaction, overall improvement and if the patient would undergo the surgery again.

RESULTS

The mean KSS improved from 61 points preoperative [standard deviation (SD) 14] to 90 points postoperative (SD 7, p < 0.001). The mean change for HKA was 6.3° (SD 3.5), for TMA 1.5° (SD 1.2) and for FMA 3.8° (SD 2.3). Postoperative leg alignment was neutral in 13 CIM BKA (50%), varus in two (8%) and valgus in 11 (42%) and patella tracking was central in 19 CIM BKA (73%) and lateral in seven (27%), respectively. Adverse events occurred in five CIM BKA: three patients required a patella resurfacing and one patient with bilateral CIM BKA needed a revision to a total knee arthroplasty. Implant survival rate was 92.3% at a follow-up of 3.2 years (SD 0.8). PROMs for CIM BKA without revision surgery were available at a mean follow-up of 3.2 years (SD 0.8). Mean pain with level walking decreased to 0.8 points (SD 1.4, p < 0.001) and mean pain with stairs or inclines to 1.6 points (SD 1.3, p < 0.001). Patient satisfaction was very satisfied or satisfied (78%), neutral (17%) or unsatisfied (4%). Overall improvement was much better or considerably better for 91% of all patients; 87% would undergo the surgery again.

CONCLUSION

A relevant change of the leg axis away from the treated femorotibial compartment due to overstuffing was observed. Although, neutral leg alignment was not restored in every case, clinical and patient-reported outcomes improved significantly. Further studies with long-term clinical and patient-reported outcomes are required to evaluate whether patients with bicompartmental knee osteoarthritis benefit from CIM BKA.

LEVEL OF EVIDENCE

IV, case series.

Partial and Combined Partial Knee Arthroplasty: Greater Anterior-Posterior Stability Than Posterior Cruciate-Retaining Total Knee Arthroplasty

BACKGROUND

Little is known regarding anterior-posterior stability after anterior cruciate ligament-preserving partial (PKA) and combined partial knee arthroplasty (CPKA) compared to standard posterior cruciate-retaining total knee arthroplasty (TKA).

METHODS

The anterior-posterior tibial translation of twenty-four cadaveric knees was measured, with optical tracking, while under 90N drawer with the knee flexed 0-90°. Knees were tested before and after PKA, CPKA (medial and lateral bicompartmental and bi-unicondylar), and then posterior cruciate-retaining TKA. The anterior-posterior tibial translations of the arthroplasty states, at each flexion angle, were compared to the native knee and each other with repeated measures analyses of variance and post-hoc t-tests.

RESULTS

Unicompartmental and bicompartmental arthroplasty states had similar laxities to the native knee and to each other, with ≤1-mm differences throughout the flexion range (P ≥ .199). Bi-unicondylar arthroplasty resulted in 6- to 8-mm increase of anterior tibial translation at high flexion angles compared to the native knee (P ≤ .023 at 80-90°). Meanwhile, TKA exhibited increased laxity across all flexion angles, with increased anterior tibial translation of up to 18 ± 6 mm (P < .001) and increased posterior translation of up to 4 ± 2 mm (P < .001).

CONCLUSIONS

In a cadaveric study, anterior-posterior tibial translation did not differ from native laxity after PKA and CPKA. Posterior cruciate ligament-preserving TKA demonstrated increased laxity, particularly in anterior tibial translation.

Robotic-arm assisted bicompartmental knee arthroplasty: Durable results up to 7-year follow-up

BACKGROUND

The purpose of our study was to investigate the mid-term clinical and functional outcomes of robotic-arm assisted Bicompartmental knee arthroplasty (BiKA).

METHODS

This study reviewed a single-centre prospectively maintained cohort of 50 patients (53 knees) who underwent BiKA (patellofemoral and medial compartment) at 5- and 7-year postoperative follow-up.

RESULTS

Mean follow-up was 7.1 ± 0.1 years (range, 7.0-7.3). Kaplan-Meier survivorship rates at 5 and 7 years were 96% and 93%, respectively. At 7-year follow-up, patient satisfaction was 76% satisfied, 13% neutral, and 11% not satisfied. Mean KSS-FS was 80.5 ± 15.8 (range, 30-100) with 82% of patients reporting walking more than 10 blocks, 89% reporting walking without support, and 100% able to go up and down stairs with 61% requiring use of a rail. Three patients (four knees) underwent revision surgery.

CONCLUSIONS

Our study reported excellent survivorship and functional outcomes, and good-excellent satisfaction at mid-term follow-up for robotic-arm assisted BiKA.

What is the Level of Evidence Substantiating Commercial Payers' Coverage Policies for Total Joint Arthroplasty?

BACKGROUND

The prevalence of total joint arthroplasty (TJA) in the United States has drawn the attention of health care stakeholders. The payers have also used a variety of strategies to regulate the medical necessity of these procedures. The purpose of this study was to examine the level of evidence of the coverage policies being used by commercial payers in the United States.

METHODS

The references of the coverage policies of four commercial insurance companies were reviewed for type of document, level of evidence, applicability to a TJA population, and success of nonoperative treatment in patients with severe degenerative joint disease.

RESULTS

282 documents were reviewed. 45.8% were primary journal articles, 14.2% were level I or II, 41.2% were applicable to patients who were candidates for TJA, and 9.9% discussed the success of nonoperative treatment in patients who would be candidates for TJA.

CONCLUSION

Most of the references cited by commercial payers are of a lower level of scientific evidence and not applicable to patients considered to be candidates for TJA. This is relatively uniform across the reviewed payers. The dearth of high-quality literature cited by commercial payers reflects the lack of evidence and difficulty in conducting high level studies on the outcomes of nonoperative versus operative treatment for patients with severe, symptomatic osteoarthritis. Patients, surgeons, and payers would all benefit from such studies and we encourage professional societies to strive toward that end through multicenter collaboration.

Does bicompartmental knee arthroplasty hold an advantage over total knee arthroplasty? Systematic review and meta-analysis

INTRODUCTION

The role of bicompartmental knee arthroplasty (BKA) in the treatment of medial patellofemoral osteoarthritis (MPFOA) has been debated by orthopaedic surgeons for years. The BKA is a cruciate ligament retaining prosthesis designed to mimic the kinematics of the native knee that requires resurfacing of only two knee compartments. In this study, we aim to assess the patient recorded outcome measures (PROMs), range of motion (ROM), perioperative morbidity, and implant revision rate in patients undergoing BKA and compare them to those undergoing total knee arthroplasty (TKA) for bicompartmental knee osteoarthritis (OA).

PATIENTS AND METHODS

We followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses Statement (PRISMA). Articles from any country and written in any language were considered. We included all randomized control trials and retrospective cohort studies examining BKA versus TKA for bicompartmental knee OA. The primary outcome measure was knee society score (KSS) at one year and the secondary outcome measures were Oxford knee score (OKS) and short-form survey (SF-)12 at six and twelve months.

RESULTS

We included five studies in our meta-analysis. In terms of OKS, KSS, and SF-12, our meta-analysis suggests better short-term results for the TKA compared with the BKA. TKA was also associated with a shorter operative time and a lower revision rate. The BKA implant did however result in marginally less intraoperative blood loss and slightly better post-operative ROM.

CONCLUSIONS

BKA did not prove to be an equivalent alternative to TKA in bicompartmental knee OA. It was associated with inferior KSS, OKS, and SF-12 at short-term follow-up and a higher revision rate.

Mid- to long-term follow-up of combined small implants

AIMS

In the last decade, interest in partial knee arthroplasties and bicruciate retaining total knee arthroplasties has increased. In addition, patient-related outcomes and functional results such as range of movement and ambulation may be more promising with less invasive procedures such as bicompartmental arthroplasty (BCA). The purpose of this study is to evaluate clinical and radiological outcomes after a third-generation patellofemoral arthroplasty (PFA) combined with a medial or lateral unicompartmental knee arthroplasty (UKA) at mid- to long-term follow-up.

METHODS

A total of 57 procedures were performed. In 45 cases, a PFA was associated with a medial UKA and, in 12, with a lateral UKA. Patients were followed with validated patient-reported outcome measures (Oxford Knee Score (OKS), EuroQol five-dimension questionnaire (EQ-5D), EuroQoL Visual Analogue Scale (EQ-VAS)), the Knee Society Score (KSS), the Forgotten Joint Score (FJS), and radiological analysis.

RESULTS

The mean follow-up was nine years (6 to 13). All scores significantly improved from preoperatively to final follow-up (mean and SD): OKS from 23.2 (8.1) to 42.5 (3.5), EQ-5D from 0.44 (0.25) to 0.815 (0.1), EQ-VAS from 46.7 (24.9) to 89.1 (9.8), KSS (Knee) from 51.4 (8.5) to 94.4 (4.2), and KSS (Function) from 48.7 (5.5) to 88.8 (5.2). The mean FJS at final follow-up was 79.2 (4.2). All failures involved the medial UKA + PFA group. Overall, survival rate was 91.5% for all the combined implants at ten years with 95% confidence intervals and 22 knees at risk.

CONCLUSION

Excellent clinical and radiological outcomes were achieved after a third-generation PFA combined with a medial or lateral UKA. BCA with unlinked partial knee prostheses showed a good survival rate at mid- to long-term follow-up. Cite this article: Bone Joint J 2021;103-B(5):840-845.

No Major Functional Benefit After Bicompartmental Knee Arthroplasty Compared to Total Knee Arthroplasty at 5-Year Follow-Up

BACKGROUND

In case of isolated medial and patellofemoral joint arthritis, bicompartmental knee arthroplasty (BCA) is an alternative to total knee arthroplasty (TKA). The purpose of our prospective, randomized study is to compare the clinical outcome of BCA vs TKA.

METHODS

Eighty patients with isolated medial and patellofemoral osteoarthritis were randomly assigned to either BCA or TKA. Patients were evaluated preoperatively, 3, 6, and 12 months, and 2 and 5 years after the procedure. Knee Society Score, Oxford Knee Score, and the University of California,Los Angeles activity scores were calculated at each follow-up; Forgotten Joint Score was assessed at final follow-up.

RESULTS

There was an improvement in Knee Society Score, Oxford Knee Score, and the University of California,Los Angeles scores in both groups but no significant differences between both groups at any follow-up. The Forgotten Joint Score at 5-year follow-up was not significantly different either. Range of motion was significantly greater in the BCA group from 1-year follow-up onward.

CONCLUSION

Our study did not show significant differences in clinical scores between BCA and TKA; only range of motion was significantly greater in BCA. Therefore, it is questionable whether this difference justifies the complexity of BCA associated with higher risk of failure. Maybe staged patellofemoral joint arthroplasty in the presence of a well-functioning UKA is an option for BCA and an alternative to revision to TKA. Long-term studies are needed to explore the potential benefits of BCA.

Management of aseptic failure of the mobile-bearing Oxford unicompartmental knee arthroplasty

BACKGROUND

Unicompartmental knee arthroplasty (UKA) accounts for 9.1% of primary knee arthroplasties (KAs) in the UK. However, wider uptake is limited by higher revision rates compared with total knee arthroplasties (TKA) and concerns over subsequent poor function. The aim of this study was to understand the revision strategies and clinical outcomes for aseptic, failed UKAs at a high-volume centre.

METHODS

This was a retrospective, single-centre cohort study of 48 patients (31 female, 17 male) with 52 revision UKAs from 2006 to 2018. Median time to revision was 67 (range 4-180) months. Indications for revision were progression of osteoarthritis (n = 31 knees, 59.6%), unexplained pain (n = 10 knees, 19.2%), aseptic loosening (n = 6 knees, 11.5%), medial collateral ligament incompetence (n = 3 knees, 5.8%) and recurrent bearing dislocation (n = 2 knees, 3.8%). Technical details of surgery, complications and functional outcome were recorded.

RESULTS

Failed UKAs were revised to primary TKAs (n = 29 knees, 55.8%), revision TKAs (n = 9 knees, 17.3%), bicompartmental KAs (n = 11 knees, 21.2%), or unicompartmental-to-unicompartmental KAs (n = 3 knees, 5.8%). Median follow up was 81 (range 24-164) months. Four patients (7.7%) died from unrelated causes. No re-revisions were identified. Surgical complications required re-operation in five knees (9.6%). Median Oxford Knee Score at latest follow up was 38 (range 9-48) points and median EQ5D3L index 0.707 (range -0.247 to 1.000).

CONCLUSIONS

Aseptic, revision UKA at a high-volume centre had good clinical outcomes. Bicompartmental KA demonstrated excellent function and should be considered an alternative to TKA for progression of osteoarthritis for appropriately trained surgeons.

Robotic arm-assisted bi-unicompartmental knee arthroplasty maintains natural knee joint anatomy compared with total knee arthroplasty: a prospective randomized controlled trial

AIMS

The aim of this study was to compare robotic arm-assisted bi-unicompartmental knee arthroplasty (bi-UKA) with conventional mechanically aligned total knee arthroplasty (TKA) in order to determine the changes in the anatomy of the knee and alignment of the lower limb following surgery.

METHODS

An analysis of 38 patients who underwent TKA and 32 who underwent bi-UKA was performed as a secondary study from a prospective, single-centre, randomized controlled trial. CT imaging was used to measure coronal, sagittal, and axial alignment of the knee preoperatively and at three months postoperatively to determine changes in anatomy that had occurred as a result of the surgery. The hip-knee-ankle angle (HKAA) was also measured to identify any differences between the two groups.

RESULTS

The pre- to postoperative changes in joint anatomy were significantly less in patients undergoing bi-UKA in all three planes in both the femur and tibia, except for femoral sagittal component orientation in which there was no difference. Overall, for the six parameters of alignment (three femoral and three tibial), 47% of bi-UKAs and 24% TKAs had a change of < 2° (p = 0.045). The change in HKAA towards neutral in varus and valgus knees was significantly less in patients undergoing bi-UKA compared with those undergoing TKA (p < 0.001). Alignment was neutral in those undergoing TKA (mean 179.5° (SD 3.2°)) while those undergoing bi-UKA had mild residual varus or valgus alignment (mean 177.8° (SD 3.4°)) (p < 0.001).

CONCLUSION

Robotic-assisted, cruciate-sparing bi-UKA maintains the natural anatomy of the knee in the coronal, sagittal, and axial planes better, and may therefore preserve normal joint kinematics, compared with a mechanically aligned TKA. This includes preservation of coronal joint line obliquity. HKAA alignment was corrected towards neutral significantly less in patients undergoing bi-UKA, which may represent restoration of the pre-disease constitutional alignment (p < 0.001). Cite this article: Bone Joint J 2020;102-B(11):1511-1518.

Clinical outcome of bi-unicompartmental knee arthroplasty for both medial and lateral femorotibial arthritis: a systematic review-is there proof of concept?

INTRODUCTION

Unicompartmental knee arthroplasty (UKA) is a well-accepted treatment for isolated unicompartmental osteoarthritis (OA) of the knee. In previous literature, it has been suggested that bi-unicompartmental knee arthroplasty (bi-UKA) which uses two UKA implants in both the medial and lateral compartments of the same knee is a feasible and viable option for the treatment of knee OA. Given the advantages of UKA treatment, it is warranted to review the literature of bi-UKA and discuss the evidence in terms of implant selection, indications, surgical techniques, and outcomes, respectively.

MATERIALS AND METHODS

Following the PRISMA guidelines, PubMed, Medline, Embase, CINAHL, Web of Science, and Cochrane Library were searched for studies presenting outcome of bi-UKA. Studies were included if they reported clinical outcomes using two unicompartmental prostheses for both medial and lateral femorotibial arthritis. Studies with the addition of patellofemoral arthroplasty or concomitant soft-tissue reconstruction and those not published in English were excluded.

RESULTS

In the early literature, the procedure of bi-UKA were performed for very severe OA and rheumatoid arthritis, but indications have evolved to reflect a more contemporary case-mix of knee OA patients. Both mobile and fixed bearing implants have been used, with the latter being the most frequent choice. A medial parapatellar approach for incision and arthrotomy has been the most frequently used technique. The present review found a promising clinical outcome of both simultaneous and staged bi-UKA although the number of long-term follow-up studies was limited.

CONCLUSIONS

Both simultaneous and staged bi-UKA has demonstrated good functional outcomes. However, the volume and level of evidence in general is low for studies captured in this review, and the data on long-term outcomes remain limited. The present review indicates that bi-UKA is a feasible and viable surgical option for bicompartmental femorotibial OA in carefully selected patients.

Unicompartmental vs. segmental bicompartmental vs. total knee replacement: comparison of clinical outcomes

Purpose

Combined medial tibiofemoral and symptomatic patellofemoral osteoarthritis is not amenable to unicompartmental knee replacement (UKR). Total knee replacement (TKR) is an invasive option in younger adults with high functional demands. The aim of this study was to compare the clinical outcome of patients who have undergone UKR, bicompartmental knee replacement (BKR) and TKR up to 2 years post-operatively.

Materials and methods

This prospective study comprised 133 subjects including 30 patients in the medial UKR group, 53 patients in the BKR group (combined medial UKR with patellofemoral joint replacement) and 50 patients in the TKR group. All subjects were evaluated using the Oxford Knee Score (OKS) and the Western Ontario and MacMaster Universities Osteoarthritis Index (WOMAC). Patients in each group were assessed using both scoring systems pre-operatively and 6 months, 1 year and 2 years post-operatively.

Results

Significant improvement of OKS was found at 6 months compared to baseline for UKR (22.7 to 38.1, p = 0.046), BKR (22.6 to 36.8, p < 0.001) and TKR (16.6 to 34.5, p < 0.001). Significant improvement was also found for the WOMAC sub-scores for all three groups during this time period. After 6 months, there was no further statistically significant improvement in either outcome score in any of the groups up to the 2-year follow-up results. There was no significant difference in either outcome score post-operatively between the three groups.

Conclusion

The magnitude of clinical improvement following knee replacement is greatest at 6 months; thereafter, only modest improvements continue to occur. This study also found no significant differences of outcomes at 2 years after surgery among UKR, BKR and TKR. BKR is a good alternative option for combined symptomatic medial and patellofemoral arthritis of the knee.

Patterns of cartilage loss and anterior cruciate ligament status in end-stage osteoarthritis of the knee

AIMS

This study aims to determine the proportion of patients with end-stage knee osteoarthritis (OA) possibly suitable for partial (PKA) or combined partial knee arthroplasty (CPKA) according to patterns of full-thickness cartilage loss and anterior cruciate ligament (ACL) status.

METHODS

A cross-sectional analysis of 300 consecutive patients (mean age 69 years (SD 9.5, 44 to 91), mean body mass index (BMI) 30.6 (SD 5.5, 20 to 53), 178 female (59.3%)) undergoing total knee arthroplasty (TKA) for Kellgren-Lawrence grade ≥ 3 knee OA was conducted. The point of maximal tibial bone loss on preoperative lateral radiographs was determined as a percentage of the tibial diameter. At surgery, Lachman's test and ACL status were recorded. The presence of full-thickness cartilage loss within 16 articular surface regions (two patella, eight femoral, six tibial) was recorded.

RESULTS

According to articular cartilage loss and ACL status, 195/293 (67%) were suitable for PKA or CPKA: medial unicompartmental knee arthroplasty (UKA) 97/293 (33%); lateral UKA 25 (9%); medial bicompartmental arthroplasty 31 (11%); lateral bicompartmental arthroplasty 12 (4%); bicondylar-UKA 23 (8%); and patellofemoral arthroplasty (PFA) seven (2%). The ACL was intact in 166 (55%), frayed in 82 (27%), disrupted in 12 (4%), and absent in 33 (11%). Lachman testing was specific (97%) but poorly sensitive (38%) for disrupted/absent ACLs. The point of maximal tibial bone loss showed good interclass correlation (ICC 0.797, 0.73 to 0.85 95% confidence interval (CI); p < 0.001) and was more posterior when the ACL was absent. Maximum tibial bone loss occurring at > 55% of the anterior to posterior distance predicted ACL absence with 93% sensitivity and 91% specificity (area under the curve 0.97 (0.94 to 0.99 95% CI; p < 0.001).

CONCLUSION

ACL status can be reliably determined from a lateral radiograph using the location of maximal tibial bone loss. According to regions of cartilage loss and ACL status, two-thirds of patients with end-stage knee OA could potentially be treated with PKA or CPKA. Cite this article: Bone Joint J 2020;102-B(6):716-726.

Customised bi-compartmental knee arthroplasty shows encouraging 3-year results: findings of a prospective, multicenter study

PURPOSE

The purpose of this study was to assess the clinical and patient-reported outcomes of a customised, individually made (CIM) bi-compartmental knee arthroplasty (BKA).

METHODS

A prospectively recruited cohort of 79 patients was implanted with a CIM-BKA (patello-femoral plus either medial or lateral tibio-femoral, iDuo G2 system, Conformis, Billerica MA) at eight centres in the US and Germany. Patients were assessed for the 2011 KSS, KOOS, and ROM pre-operatively and at 2 weeks, 6 weeks, 12 weeks, 1 year, and 2 years post-operatively.

RESULTS

The objective KSS score significantly improved from 69 at the pre-operative visit, to 94 at the 2-year post-operative time-point. Similar improvements were observed for the KSS function and satisfaction domains. Significant improvements from pre-operative levels were observed across all five domains of the KOOS. Two patients have undergone surgery to revise their CIM-BKA implant to total knees, resulting in a survivorship rate of 97.5% at an average follow-up of 2.6 years.

CONCLUSIONS

CIM-BKA compares favourably to published scores as well as revision rates for previously available monolithic OTS-BKA implants. CIM-BKA implants provide surgeons with a viable and patient-specific monolithic implant solution as an option for patients presenting with bi-compartmental disease, who might, otherwise, be treated by performing uni-condylar + patello-femoral joint or bicruciate sparing TKA surgeries. Longer follow-up and higher numbers have to be awaited for further validation of these encouraging early results.

LEVEL OF EVIDENCE

3b (individual case-controlled study).

Systematic Review of Modular Bicompartmental Knee Arthroplasty for Medio-Patellofemoral Osteoarthritis

BACKGROUND

We aimed to locate, appraise, and synthesize the available literature to assess the functional outcome of modular bicompartmental knee arthroplasty (BKA) compared to total knee arthroplasty (TKA) for medio-patellofemoral osteoarthritis.

METHODS

After an extensive literature search based on electronic databases such as MEDLINE, EMBASE, CINAHL, and PubMed, and grey literature, 9 articles satisfied our selection criteria which included 1 randomized controlled trial, 1 prospective cohort, 3 retrospective cohort, and 4 case series. Narrative synthesis was performed due to clinical, methodological, and statistical heterogeneity among the included studies.

RESULTS

There were 331 participants (341 knees) in this systematic review. BKA group included 229 patients (239 knees) and TKA group included 102 patients (102 knees). The quality of included studies ranged from moderate to very low as per GRADE (grading of recommendations, assessment, development, and evaluation working group) score with low to high risk of bias. Most of the studies showed comparable functional outcome in BKA compared to TKA such as Knee Society Score, Knee Osteoarthritis and Outcome Score, Short Form-36 score, and revision surgery in short-term to midterm follow-up. BKA patients achieved better range of movement and forgotten knee status than TKA patients. It resulted in longer operative time, but less intraoperative blood loss. Long-term series showed 95.1% survivorship of BKA at 5 years and 58% at 17 years.

CONCLUSION

Current evidence suggests that modular BKA provides comparable functional outcome to TKA at short-term to midterm follow-up, however, with poor long-term survivorship.

The Combination of Inlay Patellofemoral Arthroplasty and Medial Unicompartmental Knee Arthroplasty Versus Total Knee Arthroplasty for Mediopatellofemoral Osteoarthritis: A Comparison of Mid-Term Outcomes

BACKGROUND

To the best of our knowledge, there have been no studies in the literature related to the use of second-generation inlay patellofemoral arthroplasty and unicompartmental knee arthroplasty combination (inlay PFA/UKA) in the treatment of mediopatellofemoral osteoarthritis (MPFOA). The aim of this study is to evaluate the efficacy of inlay PFA/UKA in MPFOA.

METHODS

The study included 49 patients applied with inlay PFA/UKA because of MPFOA and 49 patients applied with TKA, matched one-to-one according to age, gender, body mass index, follow-up period, preoperative Knee Society Score, and range of motion. All the patients were evaluated clinically using the Knee Society Score, Knee Injury Osteoarthritis Outcome Score, and range of motion, and were also evaluated radiologically. Complication rates and length of hospital stay were compared.

RESULTS

The mean follow-up period was 54 ± 4 and 54.4 ± 3.9 months in inlay PFA/UKA and TKA groups, respectively. (P = .841). No statistically significant difference was determined between the 2 groups in respect of the mean clinical scores at the final follow-up examination (P ≥ .129). Total complications were fewer and length of hospital stay was shorter in the inlay PFA/UKA group than in the TKA group (P = .037 and P = .002). There was no radiographic evidence of progression of lateral compartment osteoarthritis according to Kellgren-Lawrence in any patient in the inlay PFA/UKA group.

CONCLUSION

In selected patient groups, inlay PFA/UKA is an alternative to TKA, with lower complication rates, shorter length of hospital stay, and clinical and functional results similar to those of TKA without osteoarthritis progression in the unresurfaced lateral compartment in the mid-term.

LEVEL OF EVIDENCE

III.

Classification of combined partial knee arthroplasty

AIMS

There has been a recent resurgence in interest in combined partial knee arthroplasty (PKA) as an alternative to total knee arthroplasty (TKA). The varied terminology used to describe these procedures leads to confusion and ambiguity in communication between surgeons, allied health professionals, and patients. A standardized classification system is required for patient safety, accurate clinical record-keeping, clear communication, correct coding for appropriate remuneration, and joint registry data collection.

MATERIALS AND METHODS

An advanced PubMed search was conducted, using medical subject headings (MeSH) to identify terms and abbreviations used to describe knee arthroplasty procedures. The search related to TKA, unicompartmental (UKA), patellofemoral (PFA), and combined PKA procedures. Surveys were conducted of orthopaedic surgeons, trainees, and biomechanical engineers, who were asked which of the descriptive terms and abbreviations identified from the literature search they found most intuitive and appropriate to describe each procedure. The results were used to determine a popular consensus.

RESULTS

Survey participants preferred "bi-unicondylar arthroplasty" (Bi-UKA) to describe ipsilateral medial and lateral unicompartmental arthroplasty; "medial bi-compartmental arthroplasty" (BCA-M) to describe ipsilateral medial unicompartmental arthroplasty with patellofemoral arthroplasty; "lateral bi-compartmental arthroplasty" (BCA-L) to describe ipsilateral lateral unicompartmental arthroplasty with patellofemoral arthroplasty; and tri-compartmental arthroplasty (TCA) to describe ipsilateral patellofemoral and medial and lateral unicompartmental arthroplasties. "Combined partial knee arthroplasty" (CPKA) was the favoured umbrella term.

CONCLUSION

We recommend bi-unicondylar arthroplasty (Bi-UKA), medial bicompartmental arthroplasty (BCA-M), lateral bicompartmental arthroplasty (BCA-L), and tricompartmental arthroplasty (TCA) as the preferred terms to classify CPKA procedures. Cite this article: Bone Joint J 2019;101-B:922-928.

Bicompartmental (uni plus patellofemoral) versus total knee arthroplasty: a match-paired study

BACKGROUND

Osteoarthritis (OA) of the knee, whether primary or post-traumatic, does not always involve all three compartments (tibiofemoral medial and lateral and the patellofemoral ones). Bicompartmental knee arthroplasty (BKA) was proposed as a good alternative to total knee arthroplasty when two of the three knee compartments were affected.

MATERIALS AND METHODS

We performed a retrospective comparative study collecting all BKAs performed between March 2010 and January 2016. During this period, we treated 27 patients with BKA for medial or lateral and patellofemoral OA. Seven of them were lost to follow-up and were not included in the study. Group A (BKA group) was compared to a homogeneous group of 20 patients who underwent TKA during the same period (group B).

RESULTS

Patients treated with TKA were younger than those treated with BKA (mean age 65 vs. 67.2; p = 0.2149). BKA resulted in longer mean operating time (87 vs. 82.4 min; p = 0.2983), less blood loss (413 vs. 458 ml; p = 0.0052) but higher blood transfusion rate (12 vs. 10%). Medium follow-up was 34 months for BKA group and 38 months for TKA group. No statistically significant differences were found in KSS score between the two groups (KSS score 92.3 for BKA, 94.5 for TKA; p = 0.5221; KSS function was 87.2 for BKA and 89.2 for TKA; p = 0.4985).

CONCLUSION

The most important finding of the present study was that although BKA seemed to be theoretically more favorable in terms of functional recovery and blood loss, patients of group A had lower KSS score and higher transfusion rate than those of group B. Our data confirm that BKA could be proposed as an alternative to TKA, especially in young and high-demanding patients.

Mid-Term Clinical, Functional, and Radiographic Outcomes of 105 Gender-Specific Patellofemoral Arthroplasties, With or Without the Association of Medial Unicompartmental Knee Arthroplasty

BACKGROUND

The purpose of this study is to evaluate clinical and radiographic outcomes after gender-specific patellofemoral arthroplasty (PFA) either isolated or combined with unicompartmental knee arthroplasty (UKA).

METHODS

A total of 105 PFAs in 85 patients were reviewed: 64 knees had isolated patellofemoral osteoarthritis and received an isolated PFA, and 41 knees with bicompartmental osteoarthritis were treated with medial UKA and PFA. Preoperative and postoperative clinical and functional assessment included knee range of motion, Knee Society Score, University of California Los Angeles Activity Score, Tegner Activity Level Scale, and visual analogue scale pain. Preoperative and postoperative radiographs were evaluated for patellofemoral and tibiofemoral compartment osteoarthritis, trochlear dysplasia, changes in patellar height, and signs of osteolysis.

RESULTS

At a mean follow-up of 5.5 ± 1.6 years, both groups showed improvement in knee joint range of motion (P < .001), clinical and functional Knee Society Score (P < .001), University of California Los Angeles Activity Score (P < .001 in the PFA group and P = .004 in the UKA + PFA group), and visual analogue scale pain (P < .001). There were no statistically significant postoperative differences between the 2 groups. No signs of osteolysis or subsidence were recorded. Survivorship of these 105 implants was 95.2%.

CONCLUSION

Excellent clinical and radiographic outcomes were achieved after PFA with a gender-specific implant both as isolated replacement and when combined with medial UKA. Bicompartmental replacement with small implants can be considered in patients with bicompartmental osteoarthritis and intact anterior cruciate ligament.

Current concepts for aligning knee implants: patient-specific or systematic?

Mechanical or anatomical alignment techniques create a supposedly ‘biomechanically friendly’ but often functionally limited prosthetic knee.

Alternative techniques for alignment in total knee arthroplasty (TKA) aim at being more anatomical and patient-specific, aiming to improve functional outcomes after TKA.

The kinematic alignment (KA) technique for TKA has shown good early clinical outcomes. Its role in extreme anatomical variation remains to be defined.

The restricted KA technique for TKA might be a reasonable option for patients with extreme anatomical variation.

While unicompartmental knee arthroplasty (UKA) has many advantages over TKA, the revision rate remains higher compared with TKA. One major explanation is the relative ease with which a UKA can be converted to a TKA, compared with revising a TKA. This can be considered as an additional advantage of UKA. Another reason is that surgeons favour revising a UKA to a TKA in cases of degeneration of the other femorotibial compartment rather than performing a relatively simple re-operation of the knee by doing an additional UKA (staged bi-UKA).

Cite this article: EFORT Open Rev 2018;3:1–6. DOI: 10.1302/2058-5241.3.170021

Bicompartmental knee arthroplasty vs total knee arthroplasty for the treatment of medial compartment and patellofemoral osteoarthritis

Background

Interest in bicompartmental knee arthroplasty (BKA) for the treatment of medial patellofemoral osteoarthritis (MPFOA) has grown in recent years because BKA offers a bone and ligament-preserving alternative to total knee arthroplasty (TKA). BKA only resurfaces the diseased compartments, while preserving proprioception and native knee kinematics. Therefore, the objective of this study is to assess knee function, perioperative morbidity, and implant survivability in patients undergoing BKA vs TKA for MPFOA.

Methods

The databases MEDLINE, PUBMED, and EMBASE were systematically searched. Randomized controlled trials and nonrandomized comparative studies comparing BKA with TKA for the treatment of MPFOA were included for further analysis. The primary outcome of interest was knee function. Secondary outcomes included range of movement, operation length, intraoperative blood loss, hospital length of stay, postoperative complications, and rate of revision length. The quality of evidence was evaluated using the GRADE approach. Meta-analysis was performed by pooling the results of the selected studies when possible.

Results

Six studies were selected for inclusion (4 prospective studies and 2 retrospective cohort studies). In total, 274 patients and 277 knees were included for analysis. There were no significant differences between the 2 groups at any time points in terms of knee function, length of stay, complication rate, or revision rate, when monolithic BKA designs were controlled for. BKA did result in significantly decreased intraoperative blood loss, at the expense of increased operative length compared with TKA.

Conclusions

The use of modular BKA for MPFOA is comparable with TKA in terms of short-term function, complication rate, and revision rate. BKA reduces intraoperative blood losses, but it is also more technically demanding, resulting in increased operation length. The use of modular BKA has acceptable short-term outcomes, but more long-term data are needed before it can be recommended for routine use in the treatment of MPFOA. The selection of modular BKA should be determined on a patient-specific basis. Currently, there is no evidence to suggest the use of monolithic BKA designs because of their high revision and failure rate.

Efficacy of bicompartmental knee arthroplasty (BKA) for bicompartmental knee osteoarthritis: A meta analysis

OBJECTIVE

A meta analysis to compare efficacy and safety of bicompartmental knee arthroplasty (BKA) and Total knee arthroplasty (TKA) in patients with bicompartmental knee osteoarthritis (OA).

METHOD

Electronic databases included PubMed, Embase, web of science and the Cochrane Library up to the end of July 2017 were searched. High quality randomized controlled trials(RCTs) and prospective clinical controlled trials were selected based on inclusion criteria. RevMan 5.3 were used for the meta-analysis.

RESULTS

Five studies containing 261 patients meet the inclusion criteria. Knee Society score (KSS)-Knee Score,KSS-Function Score, and flexion range of the knee in BKA group is greater than those in TKA group (P = 0.03,P < 0.0001,P = 0.0008 respectively); Hip-Knee-Ankle (HKA) angle in BKA group is smaller than TKA group (P < 0.00001); more postoperative complications are observed in BKA group (P = 0.007); no significant difference was found in proportion of revision between the two groups (p = 0.11).

CONCLUSION

Compared to TKA, BKA can bring better knee function and life quality to patients with bicompartmental knee OA. Though BKA may cause more postoperative complications, it can be an alternative treatment of TKA for patients with bicompartmental knee OA.

Bicompartmental knee arthroplasty

Total knee arthroplasty (TKA) is the most worldwide practiced surgery for knee osteoarthritis and its efficacy is mightily described by literature. Concerns about the invasiveness of TKA let the introduction of segmental resurfacing of the joint for younger patients with localized osteoarthritis. Bone stock sparing and ligaments preservation are the essence of both unicompartmental knee arthroplasty (UKA) and bicompartmental knee arthroplasty (BKA). Advantages related to BKA are the respect of knee biomechanics, lower complications rates, shorter hospital stay, faster rehabilitation. Moreover, in case of failure of the first implant the conversion to TKA is undemanding and can be compared to a standard prosthesis. Our experience suggest that BKA is a reliable technique in selected cases and especially younger people with higher functional requests can favourably profit from it. Although those results are encouraging, we still need further prospective, randomized, long-term studies to finally assess BKA indications and outcomes.

Fracture of the Tibial Baseplate in Bicompartmental Knee Arthroplasty

Introduction. Bicompartmental knee arthroplasty (BKA) addresses combined medial and patellofemoral compartment osteoarthritis, which is relatively common, and has been proposed as a bridge between unicompartmental and total knee arthroplasty (TKA). Case Presentation. We present the case report of a young active man treated with BKA after unsuccessful conservative therapy. Four years later, loosening with fracture of the tibial baseplate was identified and the patient was revised to TKA. Discussion. Although our case is only the second fractured tibial baseplate to be reported, we believe that the modular titanium design, with two fixation pegs, is too thin to withstand daily cyclic loading powers. Light daily routine use, rather than high-impact sports, is therefore advised. Failures may also be related to the implant being an early generation and known to be technically complex, with too few implant sizes. We currently use TKA for the treatment of medial and patellofemoral compartment osteoarthritis.

Long-term results of compartmental arthroplasties of the knee

Partial knee arthroplasty (PKA), either medial or lateral unicompartmental knee artroplasty (UKA) or patellofemoral arthroplasty (PFA) are a good option in suitable patients and have the advantages of reduced operative trauma, preservation of both cruciate ligaments and bone stock, and restoration of normal kinematics within the knee joint. However, questions remain concerning long-term survival. The goal of this review article was to present the long-term results of medial and lateral UKA, PFA and combined compartmental arthroplasty for multicompartmental disease. Medium- and long-term studies suggest reasonable outcomes at ten years with survival greater than 95% in UKA performed for medial osteoarthritis or osteonecrosis, and similarly for lateral UKA, particularly when fixed-bearing implants are used. Disappointing long-term outcomes have been observed with the first generation of patellofemoral implants, as well as early Bi-Uni (ie, combined medial and lateral UKA) or Bicompartmental (combined UKA and PFA) implants due to design and fixation issues. Promising short- and med-term results with the newer generations of PFAs and bicompartmental arthroplasties will require long-term confirmation.

Cite this article: Bone Joint J 2015;97-B(10 Suppl A):9–15.

Is knee function better with contemporary modular bicompartmental arthroplasty compared to total knee arthroplasty? Short-term outcomes of a prospective matched study including 68 cases

BACKGROUND

Bicompartmental knee arthroplasty (BKA) was developed to treat medial tibiofemoral and patellofemoral osteoarthritis while preserving the anterior cruciate ligament to optimise knee kinematics. Our objective here was to compare the probability of achieving forgotten knee status and the functional outcomes at least two years after BKA versus total knee arthroplasty (TKA). We hypothesised that contemporary modular BKA produced better functional outcomes than TKA after at least two years, for patients with similar pre-operative osteoarthritic lesions.

MATERIAL AND METHODS

We conducted a two-centre prospective controlled study of 34consecutive patients who underwent BKA between January 2008 and January 2011. Each patient was matched on age, gender, body mass index, preoperative range of knee flexion, centre, and surgeon to a patient treated with TKA. An independent observer evaluated all 68 patients after six and 12months then once a year. Forgotten knee status was defined as a 100/100 value of the Forgotten Joint Score (FJS-12) and each of the five KOOS subscales. We also compared the two groups for knee range of motion, Knee Society Scores (KSSs), Timed Up-and-Go test (TUG), and UCLA Activity Score.

RESULTS

At a mean follow-up of 3.8±1.7 years, the probability of forgotten knee status was significantly higher in the BKA group (odds ratio, 4.64; 95% confidence interval, 1.63-13.21; P=0.007, Chi(2) test). Mean post-operative extension was not significantly different between the groups, whereas mean range of knee flexion was significantly greater in the BKA group (130°±6° vs. 125°±8° after TKA; P=0.03). The BKA group had significantly higher mean values for the knee and function KSSs, TUG test, and UCLA score (P<0.04 for all four comparisons).

CONCLUSION

After at least two years, contemporary unlinked BKA was associated with greater comfort during everyday activities (forgotten knee) and better functional outcomes, compared to TKA. These short-term results require validation in randomised trials with longer follow-ups.

LEVEL OF EVIDENCE

III, case-control study.

Prospective randomised trial comparing unlinked, modular bicompartmental knee arthroplasty and total knee arthroplasty: a five years follow-up

BACKGROUND

A significant proportion of patients with knee osteoarthritis have articular degeneration that is limited to the medial and patellofemoral compartments. The objective of this study was to compare clinical outcomes of unlinked bicompartmental knee arthroplasty (BCA) and total knee arthroplasty (TKA) at 5years in this subset of patients.

METHODS

48 patients were randomised into two groups: unlinked, modular bicompartmental arthroplasty and total knee arthroplasty. Data on demographics and clinical outcomes were collected (Bartlett Knee Score, Oxford Knee Score, Knee Society Score). Data on intra-operative blood loss in both groups were also recorded.

RESULTS

Out of the 48 patients, 26 underwent BCA and 22 had TKA. Both groups shared similar demographic profiles. At five years post surgery, there was significant improvement across all functional scores in both groups. However, there was no significant difference in outcome scores in the BCA group compared to the TKA group. The drop in serum haemoglobin levels postoperatively was 1.55 and 2.30g/dl for the BCA and TKA groups respectively (p<.001). The total amount of blood loss was 397 and 647ml respectively (p=.001).

CONCLUSIONS

Unlinked, modular BCA results in similar clinical and functional scores as TKA for medial and patellofemoral arthritis in the mid-term. Intra-operative blood loss was significantly lower in the BCA group compared to the TKA group. BCA is a viable option for a select group of young and active patients with the advantage of reduced intra-operative blood loss and equivalent functional outcomes as TKA.

Kinematics of monoblock bicompartmental knee arthroplasty during weight-bearing activities

PURPOSE

There is an increased interest in treating arthritis of the medial and patellofemoral compartments without using a total knee arthroplasty. The purpose of this study was to measure kinematics in knees with a monoblock bicompartmental arthroplasty to see whether maintaining the cruciate ligaments and lateral compartment resulted in consistent kinematics more similar to healthy knees than those observed in replaced knees.

METHODS

The kinematics of ten knees with monoblock bicompartmental arthroplasty were observed using fluoroscopy during three weight-bearing activities. Model-image registration techniques were used to quantify the three-dimensional motions of the knee joints.

RESULTS

During kneeling, lunging, and stair-step activities, the medial condyle remained relatively close to the centre of the tibial plateau, while the lateral condyle typically moved posteriorly with flexion. Knees generally exhibited motion patterns consistent with retained cruciate ligament function, but individual patterns varied significantly.

CONCLUSIONS

Bicompartmental knee arthroplasty has the potential to retain more natural knee function. Improved tools for aligning the implants and increased implant sizing options may be required to achieve highly consistent results and realize the clinical benefit of a knee arthroplasty with intact cruciate ligaments.

LEVEL OF EVIDENCE

III.

Bi-unicompartmental and combined uni plus patellofemoral replacement: indications and surgical technique

The anatomy and orientation of the condyles and the trochlea are not standard, but related to morphotype, gender and race. Consequently, the extreme variability in their dimension, and in the distance and angle between the axis of the condyles and of the trochlea, often necessitates a "custom-made" replacement. This may be achieved through the use of small implants. Bicompartmental osteoarthritis with intact ligaments should be addressed with bi-unicompartmental (bi-UKR) or UKR plus patellofemoral replacement (PFR). These options allow selective replacement of the worn compartments and a customised fit of the small implants to the native knee anatomy. Clinical consequences are restoration of the native knee kinematics and overall better function.

Tricompartmental resurfacing arthroplasty with a follow-up of more than 30 years

BACKGROUND

Unicompartmental and patellofemoral joint replacements are proven solutions for arthritis limited to one compartment of the knee. Bicompartmental replacement has been considered lately as an alternative for combined medial and patellofemoral arthritis. The main idea behind these resurfacing solutions is tissue preservation with conservation of bone stock and both cruciate ligaments. Tricompartmental replacement with selective resurfacing of all three compartments with different modular implants is exceptional.

METHODS

The authors present a case with more than thirty year follow-up both clinically and radiographically.

RESULTS

Excellent function and patient satisfaction are observed at 30 year follow-up. Radiographs show no osteolysis or loosening of components.

CONCLUSIONS

Conservation of both anterior and posterior cruciate ligaments seems to protect against polyethylene wear at long-term follow-up.

LEVEL OF EVIDENCE

IV.

In vivo kinematics of a robot-assisted uni- and multi-compartmental knee arthroplasty

BACKGROUND

There is great interest in providing reliable and durable treatments for one- and two-compartment arthritic degeneration of the cruciate-ligament intact knee. One approach is to resurface only the diseased compartments with discrete unicompartmental components, retaining the undamaged compartment(s). However, placing multiple small implants into the knee presents a greater surgical challenge than total knee arthroplasty, so it is not certain that the natural knee mechanics can be maintained or restored. The goal of this study was to determine whether near-normal knee kinematics can be obtained with a robot-assisted multi-compartmental knee arthroplasty.

METHODS

Thirteen patients with 15 multi-compartmental knee arthroplasties using haptic robotic-assisted bone preparation were involved in this study. Nine subjects received a medial unicompartmental knee arthroplasty (UKA), three subjects received a medial UKA and patellofemoral (PF) arthroplasty, and three subjects received medial and lateral bi-unicondylar arthroplasty. Knee motions were recorded using video-fluoroscopy an average of 13 months (6-29 months) after surgery during stair and kneeling activities. The three-dimensional position and orientation of the implant components were determined using model-image registration techniques.

RESULTS

Knee kinematics during maximum flexion kneeling showed femoral external rotation and posterior lateral condylar translation. All knees showed femoral external rotation and posterior condylar translation with flexion during the step activity. Knees with medial UKA and PF arthroplasty showed the most femoral external rotation and posterior translation, and knees with bicondylar UKA showed the least.

CONCLUSIONS

Knees with accurately placed uni- or bi-compartmental arthroplasty exhibited stable knee kinematics consistent with intact and functioning cruciate ligaments. The patterns of tibiofemoral motion were more similar to natural knees than commonly has been observed in knees with total knee arthroplasty. Larger series are required to confirm these as general observations, but the present results demonstrate the potential to restore or maintain closer-to-normal knee kinematics by retaining intact structures and compartments.

Patellofemoral arthroplasty

Patellofemoral arthroplasty remains controversial, primarily due to the high failure rates reported with early implants. Several case series have been published over the years, which describe the results with various first- and second-generation implants. The purpose of this work was to summarize results published up to now and identify common themes for implants, surgical techniques, and indications. First-generation resurfacing implants had relatively high failure rates in the medium term. Second-generation implants, with femoral cuts based on TKA designs, have yielded more promising medium-term results. The surgical indications are quite specific and must be chosen carefully to minimize poor results. Short-term complications are generally related to patellar maltracking, while long-term complications are generally related to progression of osteoarthritis in the tibiofemoral joint. Implant loosening and polyethylene wear are rare. Overall, recent improvements in implant design and surgical techniques have resulted in better short- and medium-term results. But more work is required to assess the long-term outcomes of modern implant designs.